The objective of this proposal is to elucidate the mechanisms underlying the adhesive interaction between polymorphonuclear leucocytes and endothelium, as exemplified in the acute inflammatory response. The PMN normally flow freely through the circulatory system surrounded by a monolayer of endothelium. When coming in contact with an inflammatory stimulus, they adhere more firmly and emigrate out of the vessel to the area of inflammation. These same responses are seen in in vitro experiments which show that the PMN adhere to monolayers of endothelium and when either cell type is incubated with a chemotactic agent, the adhesion increases. Therefore, this investigation will contribute to a better understanding of not only the inflammatory response but also cell-cell adhesion. Specifically, the interaction will be examined with respect to (1) what is responsible for the specificity of the interaction; (2) the role of carbohydrates in recognition and adhesion; (3) what changes occur in the endothelium after binding of a chemotactic agent; (4) the effects of lipid modulation on this interaction and on the chemotactic receptor binding; (5) the formation and maintenance of junctions between the endothelial cells; (6) the localization of calcium during their interaction and after binding of chemotactic agents to the endothelium; and (7) the role of heparin, fibronectin and cyclic nucleotides. Adhesion measurements will be made using a monolayer collection assay and a novel method employing the scanning electron microscope. Cells will be analyzed using rapid freeze techniques, transmission electron microscopy, fluorescent polarization and fluorescent microscopy. Isolated membranes will be analyzed by gas, gel and thin layer chromatography, electron microscopy and Scatchard analysis of the receptors. In all instances a variety of tissue culture techniques will have to be employed. By combining these ultrastructural, biochemical and biophysical techniques, it is hoped that the structures on the surfaces of the PMN and endothelium responsible for adhesion and the specificity of adhesion will be characterized.